1. Field of the Invention
The present invention relates to a fluid pressure piston actuated control valve. More specifically, the present invention relates to a fluid pressure piston actuated control valve, where the piston has a sliding circumferential surface which is received in an inner surface of a cylindrical bore and is adapted to fuse with the inner surface of the bore at a predetermined fused temperature.
2. Discussion of the Related Art
Fluid pressure control valves are known, for example, from U.S. Pat. No. 3,982,559 to Ochs, which discloses a fluid pressure control valve that utilizes a diaphragm 34-36 to actuate a valve stem 25 to move a valve head 24 to and from the valve seat 16 to open and close the valve.
If the fluid being regulated by the valve is a flammable fluid, for example, hydrogen, natural gas, propane, etc., it is important to maintain the valve fluid within the housing to prevent the addition of fuel to the fire to reduce the likelihood of an explosion or further fueling of the fire. In the event of a fire, the temperature of the valve housing increases, which will eventually cause the elastomeric diaphragm to melt, thus providing a leakage path for the hydrogen gas, or other flammable fluid, disposed inside of the valve to leak under pressure to the atmosphere. It has been proposed to substitute a metal diaphragm for the elastomeric diaphragm. However, a metal diaphragm, while safer with respect to a fire hazard than an elastomeric diaphragm, is quite limited in its capacity ratings which limits the selection of valves to large expensive valves with very limited capacity and regulation accuracy.